1) Nothing is actually changing, per se. You've been peeing next to trans people your whole life. Policies like Target's are to show support for LGTBQ communities and to stand in opposition of the transphobic legislation that has been passed in several states.
2) These policies did not dismantle an invisible force field that was previously in place preventing trans people (or those perverts who we'll get to in a second) from entering a bathroom. Anyone can walk into any bathroom. I have accidentally walked into a men's room numerous times without anyone being like, "Oh hey! Wrong one!". And I wasn't even trying. Unless you were going to some super max bathrooms with bouncers checking IDs and birth certificates, the entry process is pretty much the same.
3) Bathrooms, especially women's, generally have several individual stalls with locks on the doors. No one can actually see anyone else pee or take a dump.
4) Bathrooms are really shitty (see what I did there?!) places to attack people. There is one entrance and exit where people come and go frequently without warning. It's a horrible place to try to do anything sketchy, from a purely strategic mindset.
5) These perverts- I have bad news- they've always been able to go into whatever restroom they want (see #2). And they can also go all kinds of other places, like dressing rooms and malls and movie theaters and pretty much any place you may also go. But don't worry, because the odds of being sexually assaulted by a stranger are pretty low. The vast majority of assault is committed by a family member or close friend.
6) If you demanded everyone pee in the restroom they were assigned at birth, ladies would be changing their tampons next to Michael Hughes. Please tell me how well that would go down.
7) When you talk about the trans community and "all those perverts" in the same argument about bathrooms, you are either a) insinuating that trans people are perverts or b) saying that trans people should be humiliated and probably beaten up or at least screamed at a lot (see #6) to prevent the made up imaginary crimes by cisgendered people. Which is bullshit.
8) Literally nothing is different except that you are now aware of the fact that a transgendered person has heard you fart, and you can either be cool or be a bigoted asshole about it.
9) Target bathrooms are no more dangerous since the policy announcement and it's absence does not make bathrooms safer. That's not how bathrooms work. They are open doors people walk through to go pee. It's not super complicated.
10) The conversations I have overheard are almost entirely about the ladies' room, yet 1 in 6 boys experience some form of sexual assault, often perpetrated by males. The fact that boys have been sharing restrooms with grown men without comment highlights the absurdity of these "safety" arguments.
Some notes for people who would like to delve a little further-
Saying bathrooms are now "unisex" or that "men" can now go to the ladies room belies a complete ignorance about what it is to be transgender. I highly recommend you educate yourself. Here is a good place to start.
Let me know if I have left anything out or if you have any additional great perspectives!